This apparatus is protective equipment to be used with a completed well. This particularly finds application in wells completed at offshore locations. Assume for explanatory purposes that a well is drilled from a jackup drilling rig or perhaps a semi-submersible drilling rig. Assume that the well is drilled in 50 feet of water or more. The vessel which supports the drilling rig remains on location during the drilling process. After the drilling process has been completed, the drilling vessel is then moved to another location to drill another well. At the time that the vessel is on location, the well may be completed, and production verified so that a production platform can be fabricated on shore to be towed to the location later.
Assume that the well is sufficiently productive that it justifies the installation of some type of production platform. In addition, well production equipment can be devised and assembled onshore and subsequently moved to the site of the well for installation onto the production platform at the well site. Without regard to the particular shape or form of the equipment or platform to be subsequently installed, it takes months, typically about one year or so, to get equipment constructed onshore and moved to the offshore location. If the water is 50 feet deep, this might require fabrication of a production platform which stands about 125 feet tall and which weighs several hundred tons. Clearly, such equipment cannot be fabricated quickly and it must be fabricated carefully, typically tailored to the precise circumstances of the particular well so that it can be towed to the location and installed. Sometimes, between 12 and 18 months will pass between the completion of the well and the installation of a permanent production platform.
It is not economically feasible to maintain the drilling rig on location until the platform has been installed. Rather, the drilling rig is moved to another well site to initiate drilling at that location. This requires that the drilling rig leave the scene and leave the well. The departure of the drilling equipment marks the end of drilling activities at the well. It is expedient for the drilling equipment, including the vessel, to be moved to another drilling site immediately after well completion so that it can economically be used in drilling another well. Preferably, the well is left with suitable casing in the hole extending to some selected depth. Production tubing is also typically installed. A conductor pipe typically surrounds the casing and extends into the seabed. For instance, the conductor pipe might be 30 inch diameter pipe and have a length of about 200 or 300 feet. The conductor pipe is typically positioned so that the top of the conductor pipe extends a distance of between 15 and 45 feet above the still water line.
The well is then shut in by installing suitable closed valves or plugs in the well. The drilling vessel departs the area and hence leaves the well substantially unprotected wherein the casing located in the larger conductor pipe is exposed to some degree of risk until the production platform can be fabricated and installed. The conductor pipe may be unsupported for a length of between 30 and 125 feet inclusive, or even longer.
Various methods have been employed to protect and support offshore wells during the period between drilling and installing a permanent platform. Some wells are cut off just above the mud line and then completed after the permanent platform has been set. Others are supported by large diameter caissons or conductor pipe. Some prior art methods include the installation of a caisson before the well is drilled. If a dry hole is drilled, the cost of the caisson in addition to the normal dry hole expenses are incurred. Other prior art methods include the installation of mud line suspension equipment, leaving the wells free standing and virtually unprotected and unsupported until a permanent platform can be installed. A well left unprotected for a long period of time can be severely damaged from hurricanes or winter storms which may occur while the well is unprotected.
The equipment of the present disclosure is a protective structural system for the otherwise free-standing conductor pipe which visibly extends from the mud line to a predetermined point above the water line. Assume that the conductor pipe protrudes from the seabed, perhaps standing 30 feet above the water line. It is vulnerable to damage from navigating ships in the area, and particularly can be damaged by extreme lateral loads caused by winter storms and summer hurricanes when left unprotected. The present apparatus is a protective structural system which fastens temporarily or permanently onto the conductor pipe. The conductor pipe is typically in the range of about 26 to about 30 inches in diameter and has wall thickness of about one inch. It is susceptible to bending and damage when left unprotected. The conductor pipe is encased and structurally supported by the present system.
The well support system of the present disclosure incorporates a steel tubular split vertical clamp, adapted to securely clamp to the protruding conductor pipe. The conductor clamp is divided into two similar pieces, split along the length thereof, and the two pieces have edge located flange plates which are joined by suitable nuts and bolts. Moreover, the conductor clamp at the lower end is connected with and braced to a rectangular frame suitably fastened to the seabed or to a supporting substructure. It is held in place by piles which are driven through the corners. Moreover, the upper end of the conductor clamp is laterally supported by diagonally positioned braces, the braces extending from the top of the clamp to the pile anchor sleeves at the corner and anchored to the seabed. The clamp is split into two halves along its diameter and the two halves are bolted together surrounding the conductor pipe.
In an alternate embodiment, the well support system of the present disclosure incorporates a permanent support frame for single or multiple wells. The completed well support system is constructed with fabricated modules which clamp tightly around the well conductor pipe. The components of the system include modules for forming a boat landing which may be secured or clamped about the conductor pipe. For multi well configurations, the system can support a deck large enough to accommodate wireline or through-tubing workover units plus a crane large enough to lift such units from a supply boat onto the deck. Thus, eliminating the need for a jackup unit for most routine well workover and maintenance operations. A miniplatform may also be supported on a single well. A cantilevered halideck supported on single or multi well configurations simplifies transportation to and from the location for site supervision and work.
The well support system of the present disclosure may also be used as a temporary support incorporating outrigger modules which may be secured to the support frame clamped about the conductor pipe. Cables secured to the outrigger module and the bottom of the boat landing temporarily provide lateral support while a permanent platform or support system is being fabricated. This system is particularly useful for temporary support of well sites being developed for installation of a complete production platform.